As shown in FIG.1, the U.S. patent application Ser. No. 08/672,859, filed by the same inventor as the present invention discloses a socket 20 having a fitting end 22 which is provided in the inner wall thereof with two grooves 221 disposed diametrically opposed relative to each other. The fitting end 22 is further provided in proximity of one end thereof with a circular slot 222. An elastic wire 24 is fitted into the fitting end 22 of the socket 20 such that a retaining side 241 of the elastic wire 24 is retained in the grooves 221 of the fitting end 22, and that an end portion 244 of the elastic wire 24 against the circular slot 222 of the driven end 22. As a result, a protruded edge 242 of the retaining side 241 of the elastic wire 24 is capable of retaining a nut which is engaged with the driven end 22 of the socket 20. In the meantime, the retaining side 241 is capable of preventing the elastic wire 24 from slipping out of the socket 20 at the time when the nut is taken out of the socket 20. As shown in FIG. 2, the structural integrity of the socket 20 can be undermined by the grooves 221 in the process of making the socket 20 by forging.